How to check if postfix is accepting external mail deliveries

To check if Postfix is accepting external mail deliveries, you can perform the following steps:

1. Check the Postfix configuration: Make sure that the mydestination parameter in the Postfix configuration file (/etc/postfix/main.cf or /etc/postfix/main.cf) is set to $myhostname or a specific hostname that matches the hostname of your mail server. This ensures that Postfix is configured to accept mail for your domain.

2. Check the Postfix status: Run the command postfix status to check the status of the Postfix service. If Postfix is running and accepting mail, you should see a message indicating that it is "running" or "active".

3. Check the Postfix logs: Look for errors or warnings in the Postfix logs to see if there are any issues with accepting external mail deliveries. You can check the logs by running the command postlog -p postfix or tail -f /var/log/mail.log (depending on your Linux distribution).

4. Use the telnet command: Use the telnet command to test if Postfix is accepting mail from an external source. Replace yourmailserver.com with your actual mail server hostname:

   telnet yourmailserver.com 25

   If Postfix is accepting mail, you should see a response like:

   220 yourmailserver.com ESMTP Postfix

   If you see an error message or no response, it may indicate that Postfix is not accepting mail from external sources.

5. Use a mail client or a tool like msmtp: Use a mail client like Thunderbird or Outlook to send an email to your mail server. If Postfix is accepting mail, you should receive the email successfully. Alternatively, you can use a tool like msmtp to send a test email:

   msmtp -v -a yourmailserver.com -t "Test email"

   If Postfix is accepting mail, you should see a response indicating that the email was sent successfully.

If you're still having issues, you can try checking the Postfix configuration files, restarting the Postfix service, or seeking help from your system administrator or a Postfix expert.